In recent years, an organic EL (electro luminescence) display device has been attracting attention as a thin, lightweight, and fast response display device. The organic EL display device includes a plurality of pixels arranged two-dimensionally. Typically, the pixel of the organic EL display device includes one organic EL element and one drive TFT (thin film transistor). The organic EL element emits light at luminance in accordance with an amount of a current passing therethrough. The drive TFT is provided in series with the organic EL element, and controls the amount of the current flowing through the organic EL element.
Variation is caused in characteristics of the elements in the pixel during manufacturing. Moreover, the characteristics of the elements in the pixel fluctuate as time proceeds. For example, characteristics of the drive TFT deteriorate individually in accordance with light emission luminance and light emission time. The same holds true for characteristics of the organic EL element. As a result, even when the same voltage is applied to gate terminals of the drive TFTs, variation is caused in the light emission luminance of the organic EL elements. Thus, in order to perform high image quality display in the organic EL display device, there is known a method in which a video signal is corrected so as to compensate for variation or fluctuation in the characteristics of the organic EL element and the drive TFT. For example, Patent Document 1 describes an organic EL display device in which a drive current is read out to an outside via a power supply line, a gain for correction and an offset for correction are updated based on an amount of the measured drive current, and the video signal is corrected using these data.
Moreover, when the same image is displayed in the organic EL display device for a long time, the characteristics of the elements in the pixels fluctuate in accordance with a pattern of a display image, and its influence may appear in a display screen. This phenomenon is called burning. For an organic EL display device configured to prevent the burning, the following techniques have been conventionally known. Patent Document 2 describes a display device in which deterioration characteristics of the light emission luminance of the pixel are obtained based on the video signal and the like, and the video signal is corrected so that the light emission luminance changes smoothly in the vicinity of a boundary of the deterioration characteristics. Patent Document 3 describes a light emission-type display device in which a target chromaticity is set so that deterioration characteristics of each color of organic EL are equal, and an input image signal is corrected so that a chromaticity of a burning prevention target portion becomes close to the target chromaticity. Patent Document 4 describes a burning phenomenon correction method in which a difference between a deterioration amount of a correction target pixel and a deterioration amount of a reference pixel is accumulated, and whether or not an input signal is to be corrected is switched in accordance with whether an accumulated amount is increased or decreased by an addition this time.